If you connect they usually schedule the connection in Sacramento instead of Emeryville. You could book EMY and if the CS is running late you could hop of at SAC or MTZ if you are worried about the connection. If you do that just let Amtrak know what you are doing.
As of recent the connection should not be much of a problem. The CS has generally arrived before the CZ departs. They will try to hold the CZ in the yard unless the CS is running more than 30 minutes late as both trains are scheduled to use track 1 at EMY. If the CS is running late it will pull into track 2 and double stop (as it did today) with sleepers off boarding first followed by the coaches when the train pulls up. The CZ will usually be boarding on track 1 so you can just hop of one and on the other.
The CZ generally pulls out of the yard between 830 and 845am to arrive for boarding in EMY by 850am or so.
It is a close connection for an LD train but it really is up to you but I personally would do it (I'm the type that generally arrives to the station no earlier than 5 minutes prior to departure at most though).
If you are in the mood to explore the Hyatt House just across the pedestrian bridge from the station. Breakfast is usually provided there at the hotel. Just be mindful breakfast is not available on the CS leaving EMY so on the CS before you leave or at the Hyatt House would be best.
It is up to your personal choice but a same day connection is allowed and doable and as long as Amtrak allows it as a scheduled designated connection they still need to get you to where you are going somehow or advise you to get off the train in SAC instead of EMY.
Amtrak will book your connection in SAC unless you specify otherwise. If you would like EMY you would have to book it separately and do so at your own risk. Try asking for MTZ if you would like to minimize your connection time with a more Amtrak approved connection
